Electrical timing control



Dec. 19, 1950 H. l. sTANBAcK ETAL 2,534,385

ELECTRICAL TIMING CONTROL Filed March 2, 1949 @df/M 42, the primary oftransformer 39 being connected to the supply across lines I.

Connected back to back with the electric discharge tube 4D is a secondtube 45, these discharge tubes serving to pass both half cycles ofsupply current through the load represented by the welding transformer10 supplying a welding load at 44. Electric discharge tube 45 is red bycomponents similar to those set forth with respect to tube 48, theseconstituting the firing capacitor 52, the discharge valve 46 andcharging valve 38.

To secure proper firing of the charging valve 38, the secondary output`of transformer 31 is fed across a capacity 41 in the grid circuit ofvalve 38, in series with the elements supplying valve 25 conducts,because its cathode is at the full negative potential of capacitor I5while its grid 21 is at approximately one-third of the negativepotential of capacitor I6, being electrically connected to approximatelyone-third point of capacitor-bridging resistor 2|. Control grid 21 ispositive, therefore, with respect to cathode 26 and will remain so untilcapacitors I5 and I6 discharge to the cross-over point, where the pothehold-off bias and constituted .by the secondary of transformer 5| andthe capacitor `48 by passed by resistor 49. The capacitor 41 is bypassedby the discharge resistor 6|. In series with the ring capacitor 52 andthe valve 38 are the contacts 62 of the thermal flow switch.

The heaters for the thermal flow switches, whose contacts are shown at68 and 62, are shown at 55 connected in series with each other andthrough the primary of transformer 54 to a tapoff point of an autotransformer 53 connected across lines I. The secondary output oftransformer 54 is fed through the cathode heaters or filaments of therectifier tube I8.

' In the drawing, the surge by-pass capacitors -tor 1, consisting of theD. C. voltage due to grid rectification plus the A. C. output oftransformer 2,to the sawtooth voltage of capacitor II plus the steady D.C. voltage of capacitor 8. Valve l5 res at the next sawtooth peak gridvoltage lafter closure of the initiating switch 3. Valve 5 ceases toconduct as soon as timing capacitors I5 and I6 are charged, capacitor 8being rapidly discharged through resistor I1. This leaves at vthe grid 4of valve 5 only the capacitor II sawtooth voltage which is alwayssufficiently negative to prevent conduction of valve 5, which will,therefore, conduct for only a portion of a half cycle'for each closureof the initiating switch 3. While valve 5 conducts, capacitors I5v andI6 are charged through rectifier tube I8, said capacitors being chargedat the same time from the same voltage source, both charging circuitshaving the same impedances. Therefore, capacitors I5 and I6 are chargedto the same voltage and then effectively disconnected from the supplytransformer I9 as valve 5 ceases to conduct. Capacitor |6 dischargesvery slowly through the voltage dividing resistor 2|; capacitor I5discharges more quickly through the fixed resistor 63 and the weld timeadjustment resistor 22.

Transformer 23 is so disposed as to make the anode 24 of valve 25negative with respect to cathode 26 during the period of conduction ofvalve 5 and rectifier tube I8. As soon as anode 24 becomes positive withrespect to cathode 26,

tential of capacitor I5 is equal to that at the tap on thecapacitor-bridging resistor 2| and subsequent positive potentials of theanode 24 with respect to cathode 25 will not re the valve 25. Timemeasuring valve 25 will conduct, therefore, on the next half cycle aftervalve 5 -and tube I8 conduct and will continue to conduct during eachhalf cycle during which anode 24 is sufficiently positive with respectto cathode 26 until the above mentioned cross-over point is reached.Conduction of valve 25 energizes coupling transformer 29 which deliversto the grid circuit of valve 3| a measured number of pulses equal innumber to the number of full cycles o Weld time desired.

Grid of charging valve 3| receives A. C. hold-off voltage fromtransformer 32 output plus a D. C. component across capacitor 33 whichis charged by valve 3| grid rectification. Each output pulse fromcoupling transformer 29 charges energy into capacitor 34. This energy isdischarged into vthe circuit of grid 35 at the be'- ginning of thefollowing half cycle, providing a voltage signal which overcomes thehold-off bias on grid 35 and causes valve 3| to conduct;

Conduction of valve 3| chargesrlng capacitor 35 through currenttransformer 31. Each time capacitor36 is charged, valve 3| conductioncurrent energizes transformer 31 and the output -tor 38, the 'igniter 51and mercury cathode pool 58 of discharge tube 40. Resistor 5|) andinductor 38 serve to shape the discharge pulse of capacitor 36 for bestfiring performance, the high current pulse produced by the dischargeserving to initiate conduction of tube 4|) in conventional manner.

Discharge tubes 40 and 45 accomplish the function of switching theprimary current to the Welder transformer 10, being connected back toback in series with one power line to the Welder transformer and servingin effect as a single pole contactor. Y

The circuits for valves 38, 46 and tube 45 are substantially the same asthe previously described circuits for valves 3|, 43 and tube 40respectively. Valve 38 lires in response to the output pulses oftransformer 31 which occur each time valve 3| conducts. Each of thesepulses charges energy into capacitor 41, this 4energy being dischargedinto the grid circuit of valve 38 at the beginning of the following halfcycle, providing a voltage peak which overcomes the hold-olf bias due tocapacitor 48, resistor 49, and transformer 5|. When valve 38 fires, itcharges ring capacitor 52, the firing capacitor being discharged byconduction of valve 46, to effect conduction of mercury pool tube in thesame manner as.' previacens-so ously described* Tor the interacliion--cf capacitor 36', vvalve 43 vand imercury'jpooltiibe L As maybe Iseenreference toy Figure' 2, the time during which tube "25 "willyfcol-'ld-uct, or lin other' terms, vthe time vduring which Weld-ing-cur ren't mayiilow V'does not vary with fluctuation the supply voltage.The dotted Waves Vl and V2 Arepresent supply voltage of highand low'values respectively. Ci' land -GII represent-:the potentials yci thecathode and grid, respectively, lof valve 25 after `the timing`'capacitors VTE fand- 1:6 have 'been charged 'by' a voltage 'supply-wave of a 'high value, such 'as' that represented by dottedsupply'voltage wave VI, C2 and G2' 'correspondingly represent thepotentials 4'of v*the catht ode and r`grid, respectively, ci valve 25fa'fter'the timing capacitors i5 Jand 1lli have been charged a 'voltagesupply Awave of" relatively lovv value,- such as* that represented 'byJdottec'l sine wave VL 'Valve 5 lvfhich 'charges'capacitors I5 and '|56is cut off Vand ceases to'conductwhen the-rca-pacitors have been chargedy'and remains non-conducting until'the initiating switch i8 is againoperated. Capacitors "f5 and I6 are, therefore, eiectivly disconnected`from the vsupuply during the `disl charging or timing 'period -so thatthe timing period isv vsubstantiall-y independent'of 'variations' ofvoltage therein.

It `will 'be seen, "therefore, that under vdifferent orvaryingconditions of supply voltage, the "time f `required for-thepotentials 'fof the grid -andcathode of the Ytiming value i5l 'tobecome equal is substantiallythesame. "Therefore for any'se'tting of`the bleeder "resistor 2'2, the tim-ing `valve- 25 will conductduringsubstantiallythe same length of time regardless of variations Tin 'the-supply voltage.

The *'xed `resistor Llili '--in 'thefg'r'id circuit of valve 25- 'is `ofhigh value rto `insure 'that any cross bleeding between the timingl'capacitors during the timing period is negligible. *The resistor 6'4'which parallels the Vcapacitor t6- is also of high value and l'serves'to admit `a "grid hold-oli' 'bias-to the grid of valve 2'5 iduring theperiodfduring :which the 4timing capacitors Iare not charged.

- 'While certain preferredem'bodiments oflthevi-n- Y vention have beenVspecifically disclosed, it is nn- Jderstorui that the vinvention Vitnot limited thereto, as 'many variations 'will lbe readily `apparent 'tothosey `skilled in the art and `the 'invention is `vtofbe given its'broadest possible interpretation within the terms -of fthe followingclaims.

'What Visfclairned is:

1. In an Av'electrical timing' system, a pair of capacitors, means hfor'charging said capacitors to the-same'vol-tage, -means for-adjustablydischarging at'leastlon'e of said capacitors, 'said ila-stenen- 'tionedmeans being capableof varyingithe difference *in discharge-rates "of`said capacitors, 'and means connected to said capacitors and responsiveEto the 4difference `in voltage Athereon 'to determine the timingperiod.

2. In qan Velectrical timing system, ta, pair voft capacitors, 'meansfor charging said ucapacitors lsi- Vn'm'ltaneously to the same voltagefrom the'sanre source, means for adjustably discharging at least oneof isaid capacitors, :said fla-st mentioned means being capable of vary-ingthe difference vvindis- 'charge v'rates of ysaid capacitors, and meansvconnected to said capacitors and responsive -tc'the difference inrvoltage thereon to determine the 'timing period.

.3. In an rrelectrical Atiming system, a pair of 'capacitors, means 4for'charging nsaid capacitors si- `mu'ltaneously f'to the *same voltageyfrom 'the same :source, .rnezamsI for slowly discharging-ione or :saidcapacitors,` means "for vdiscl'iarging the `other .of Lsaid 'capacitorsmore rapidly, said last mentioned means"being variable for adjustablydischarging sai-dother capacitor, and means-connected tofsaid capacitorsand vresponsive 'to the -diference'-in voltage thereon todetermine theitirning period.

4. In :an electrical timing system,-'a pair :of Vcapac'itors, means forcharging said 'capacitorsfs'imultaneously to the same voltageAfrornjthesame source,v means including vva high resistance parallelingAone of rsaid' 'capaci-tors, means including :a variable 'resistorvparalleling 'the other oi lsaid ca Ipacitors fior adj us'tablydischarging `said other rcapacitor, and means connected iso-saidcapacitors rand responsive tothe difference in voltage lthereon todetermine the timing period.. y

1I-n fain-electrical timing system, a pair lof fcapacitors, fof thev"saine capacity, means `for charging said capacitors to thesamevoltage, means iin cluding fixed bleeder resistances'paralleling'each of said capacitors, means including a variable resistanceparalleling one of said capacitors :and

variable to affect a linear change in timing vfor a linear change inresistance, and means Aconnected vitc `said capacitors and responsive to`.the di-ierence in voltage thereon to determine the timing `period.

6'.v Inf'fan electrical timing system, fa pairo'ffcapacitors of lthe--same capacity, .means 'for charging `said capacitors :simultaneously.to the same voltage `from the same source, means including a voltagedivider paralleling lone -of :said capacitors, means including "avariable lresistor parallel# ing 'the other of said -capacitors andcapable fof varying 'the 'difference in discharge rates oi saidcapacitors, and means `responsive -to the diierence between the voltageof a point on said Avoltage divider and the voltage-oi said othercapacitor to vdetermine 'the'timing period.

7. VIn van electrical timing system, a pair of capacitors oi y'the samecapacity, means for charging :said capacitors :simultaneously lto thesame voltage from the same source, `means including fa resistive voltagedivider p'aralleling one of said capacitors, means including a .resistorof substantially the fsame resistance `as said voltage l'dividerparalleling the other of sa-id capacitors, means including a variableresistor `also paralleling said other capacitor and variable to 'eect a'linear change in timing lfor ia linear Achange in resist ance, @andmeans :responsive tothe difference ibetween ithe voltage of a point onsaid voltageadi- Vider and the voltage of said -other capacitor 'itdetermine the timingzperiod. Y 8. `In .an electrical timing system, -apair of feapactors --of the same capacity, Ameans -for ncharg ing vsaidcapacitors lsimultaneously to the same voltage :from Athe same source,means including a resistance voltage divider paralleling one of saidcapacitors, means including a resistor of substantially 'the sameresistance as said voltage divider -paralleling the other of saidcapacitor, meansincluding a variable resistor also parallelfing Asaidother 'capacitor and variable to eiectfa linear `change in timing for a'linear change fin resistance, :an electric valve, and means-connectingsaid electric valve vto a point on said voltage divider and to saidother capacitor so that v'the conduction of said valve is dependent uponvthe difference betwecn'the voltages 'of said point and of said othercapacitor. Y 9. 'In an electrical timing system, a pair loi?.

capacitors, :means for charging said capacitors to Athe 'same voltage,y:means including va y'voltage divider paralleling one of saidcapacitors, means including a variable resistor paralleling the other ofsaid pair of capacitors and capable of varying the difference indischarge rates of said capacitors, an electric valve, and meansconnecting said electric valve to a point on said voltage divider and tosaid other capacitor so that the conduction of said Valve is dependentupon the difference between the voltages of said point and of said othercapacitor.

10. In an electrical timing system, a pair of capacitors, means forcharging said capacitors simultaneously to the same voltage from thesame source, means including a voltage divider paralleling one of saidcapacitors, means including a variable resistor paralleling the other ofsaid pair of capacitors and capable of varying the difference indischarge rates of said capacitors, an electric valve, and` meansconnecting said, electric Valve to a point on said voltage divider andto said other capacitor so that the conduction of said valve isdependent 'upon the difference between the voltages of said point and ofsaid other capacitor.

11. In an electrical timing system, a pair oi capacitors, means forcharging said capacitors to the same voltage, means including aresistive voltage divider paralleling one of said capacitors, meansincluding fixed and variable resistors paralleling the other of saidcapacitors, said ixed resistor being of substantially the sameresistance as said voltage divider, said variable resistance effecting alinear change in timing for a linear change in resistance, an electricvalve, and means connecting said electric valve to a point on saidvoltage divider and to said other capacitor so that the conduction ofsaid valve is dependent upon the diierence between the 'voltages of saidpoint and said other capacitor. l

12. In an electrical timing system, a pair of capacitors, means forcharging said capacitors to the same voltage, means for adjustablydischarging at least one of said capacitors, said last mentioned meansbeing capable of varying the diiierence in discharge rates of saidcapacitors, an

electric valve, and means connecting elements of said electric valve tosaid capacitors so that'the conduction of said valve is determined bythe difference in the voltages of said capacitors.

13. In an electrical timing system, a pair of capacitors, means forcharging said capacitors simultaneously to the same voltage from thesame source, means for adjustably discharging at least one of saidcapacitors, said last mentioned means being capable of varying thedifference in discharge rates of said capacitors, an electric valve, andmeans connecting elements of said electric valve to said capacitors sothat the conduction of said Valve is determined by the difference in thevoltages of said capacitor.

14. In an electrical timing system, a pair oi capacitors, means forcharging said capacitors, means for adjustably discharging at least oneoi said capacitors, said last mentioned means being capable of varyingthe difference in discharge rates of said capacitors, and meansconnected to said capacitors and responsive to the difference in voltagethereon to determine the timing period.

15. In -an electrical timing system, a pair of capacitors, means forcharging said capacitors, means for adjustably discharging at least oneof said capacitors, said last mentioned means being capable of varyingthe difference in discharge rates of said capacitors,l anelectricpvalve, and

means connecting elements of said electric valve to said capacitors sothat the conduction of said valve is determined by the difference in thevoltages `of said capacitors.

16. In `an electrical timing system, a pair of capacitors, means forcharging said capacitors, means for adjustably discharging at least oneof said capacitors, said last mentioned means being capable of Varyingthe difference in discharge rates of said capacitors. and meansconnected `to `Said capacitors and responsive to the diii'erence involtage thereon to determine the timing period, said charging meansincluding initiating means providing for the passage of but a singlecharging pulse until the initiating means is reactuated.

17. In an electrical timing system, a timing circuit, an electric` valvecontrolling the energization of said timing circuit, a grid biasnormally imposed on the control .grid of said valve and `constituted bythe resultant of at least iirst and second added capacitors and a thirdopposed capacitor, the first vand second added capacitors normallymaintaining a negative bias onthe control grid at least while the valveanode is positive, means for charging said capacitors, initiating meansfor the timing circuit including means for interrupting the charging ofsaid first and third capacitors, means for quickly discharging the rstcapacitor so that the third capacitor overrides the second capacitor toprovide for conduction of the valve for a single half cycle, and meansdischarging the third capacitor when the valve conducts so that thesecond capacitor alone has control of the valve grid to preventconduction ci. the valve thereafter until the initiatin means isreactuated.

`i8. In an electrical timing system, 4a timing circuit, an electricvalve controlling the energication of said timing circuit, a grid biasnormally imposed on the control grid of said valve and constituted bythe resultant of at least nrst and second added capacitors and a thirdopposed capacitor, means connecting said iirst capacitor Vsuch that saidcapacitor is charged by grid rectification of said valve, meansincluding rectifiers charging said second and third capacitors, the rstand second added capacitors normally maintaining a negative bias on thecontrol grid at least While the valve'anode is positive, initiatingmeans including means for interrupting the Voltage supply to said firstand third capacitors, means for quickly discharging the rst capacitor sothat the third capacitor overrides the second capacitor to provide forconduction of the valve for a single half cycle, and means dischargingthe third capacitor when the valve conducts so that the second capacitoralone has control of the valve grid to prevent conduction of the valvethereafter until the initiating means is reactuated.

19. In an electrical timing system, a timing circuit, an electric valvecontrolling the energization of Said timing circuit, a grid biaisnormally imposed on the control grid of said valve and constituted bythe resultant of at least rst and second added capacitors and a thirdopposed capacitor, means connecting said rst capacitor such that saidcapacitor is charged by grid rectiiication of said valve, meansincluding rectiers charging said second and third capacitors, the firstand second added capacitors normally maintaining a negative bias on thecontrol grid at least while the valve anode is positive, initiatingmeans including means for interrupting the voltage SupplytLSais1fi1St-and third. capacitors 9 v means including a circuit ofrelatively low resistance for discharging said rst capacitor so that thethird capacitor overrides the second capacitor to provide for conductionof the valve for a single half cycle, means for discharging said thirdcapacitor including a circuit of relatively low resistance connectedthrough the valve circuit so that after the valve conducts the secondcapacitor alone has control of the valve grid to prevent conduction ofthe valve thereafter until the initiating means is reactuated.

20. In an electrical timing system, a timing circuit including a pair ofcapacitors, means including an electric valve controlling the chargingof said capacitors, means for slowly discharging one of said capacitors,means for discharging the other of said capacitors more rapidly, saidlast mentioned means( being variable for adjustably discharging saidother capacitor, and means connected to said capacitors and responsiveto the difference in voltagethereon to determine the timing period, agridbias normally imposed on the control grid of said valve andconstituted by the resultant of at "least additional rst and secondadded capacitors and a third opposed ca- 25 2,454,167

10 pacitor, the first and second added capacitors normally maintaining anegative bias on the control grid at least While the valve anode ispositive. initiating means for the timing circuit including means forinterrupting the charging of said rst and third capacitors, means forquickly discharging the iirst capacitor so that the third capacitoroverrides the second capacitor to provide for conduction of the valvefor a single half cycle, and means discharging the third capacitor whenthe valve conducts so that the second capacitor alone has control of thevalve grid to prevent conduction of the valve thereafter until theinitiating means is reactuated.

' HARRIS I. STANBACK.

ERNEST G. ANGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Woll Oct. 15, 1946 Hartwig Nov. 16, 1948Number

